Vapor control



C. D. LAIDLEY VAPOR CONTROL Filed Sept. 14( 1948 Nov. 6, 1951 A INVENTOR, knee-c5 D. mo/ EH BY #Ww indicated at II. This vacuum and pressure relief valve is of a conventional type of construction designed to permit escape or egress of gas from the vent line I to an outlet I2 whenever the pressure in the vent line exceeds a predetermined value and to permit of ingress of gas or air to the vent line I0 whenever the pressure in the vent line becomes negative pressure or subatmospheric. As typical of the various situations that might occur in batteries of storage tanks, the tank C is illustrated as being filled with crude oil, the incoming oil being discharged into the tank such as through a conduit I3. Tank A, on the other hand, is illustrated as being emptied or run through the outlet I4. Tank B is illustrated as having been filled with crude oil and functioning merely as a storage tank, the inletvr and outlet being closed. The hatch covers I5 of all tanks are illustrated as being closed Yas this is their normal position except when gauging or thieng At the point of communication between each tank and the vent line I0 there is disposed a pressure actuated or diaphragm actuated balanced valve one form of which is illustrated in Fig. 2. This consists generally of a body indicated at 20 through which Vthere extends a conduit 20a which-forms a part of the vent line being connected to sections of the vent line I0 in any suitable manner such as that illustrated. In the top of the conduit 20a there is a circular seat or opening 2l for a balanced valve of the butterfly or damper type indicated at 22. This valve may have a sealing gasket 22a around its edges engageable with the walls of the opening 2| to form la substantially leak proof seal therewith. The

valve 22 is mounted for swinging movement on transverse pintles 23 and is connected through a link 24 to an arm 25 on a stem 26. The stem 26 is connected to a diaphragm 21 consisting merely of a sheet of rubber or equivalent flexible material having its edges clamped between parts of the housing 20 and reenforced adjacent its center by means of opposed plates 28. The under side of the diaphragm is exposed through aperture 29 to the pressure existing within the tank with which the valve is associated. The pressure within the tank is conducted from the top of the tank through the opening 30 in the bottom of the housing and upwardly around the sides of the conduit 20a as illustrated in Fig. 3. The upper side of the diaphragm is exposed to atmospheric pressure conducted thereto through a vent 3 I.

At the top of the housing there is an adjustable stem 32, the head 33 of which serves to support a hanger 34 for a weight 35 that is engageable with the upper side of the diaphragm formed of the rubber sheet and the opposed plates 28. The diaphragm is urged upwardly against the under side of this weight by means of a weak compression spring 36 which is seated on the partition 31 in which the aperture 29 is formed.

The operation of the above described construction is substantially as follows. While the tank C is being filled as illustrated the incoming oil filling the tank tends to displace the air or vapor in the top of the tank and as the filling proceeds this pressure gradually increases. The increase of pressure becomes eiective onl the under side of the diaphragm 21 being conducted thereto through opening 30 and aperture 23. As long as the pressure in the tank does not become excessive or rise beyond a predetermined degree the diaphragm 21 will merely rise until it en'- gages the weight 35 without raising the weight from its lowermost position wherein it is suspended by its hanger 34 from the head 33. In this position the stem 26, arm 25 and link 24 hold the valve 22 in its horizontal or closed position. However, whenever the pressure in the tank exceeds a predetermined value so that the force asserted thereby on the diaphragm 21 is sufiicient to elevate the weight 35 the diaphragm will then cause an opening ofthe valve 22 by swinging it into the dotted line position indicated at 38. When the valve 22 is opened in this manner excessive pressure in the tank C will be released therefrom into the vent line I0 through which it may be conducted to another tank which is decient in Vpressure or the vent line I0 may function merely as a storage reservoir for excessive pressure.

Considering the tank A which is being emptied of crude oil therein the pressure in the vapor space of this tank may be atmospheric or even subatmospheric. Whatever value the pressure may be within the tank A below the pressure existing in the vent line I0 the differential in pressure between the vent line and the tank A is incapable of opening or influencing the valve 22 because of its balanced nature. In other words, if the pressure in the vent line I0 is considerably greater than the pressure within the housing 20 associated with tank A this pressure is effective on the valve 22 on opposite sides of the pintles 23 and does not cause the valve to open. Consequently, it is immaterial to what extent the pressure in the vent line Il) is greater than the pressure existing in the tank A above a predetermined negative pressure. The valve 22 will not open to allow tank A to rob pressure from the vent line or from tanks B or C. If the pressure in tank A should become negative pressure or should fall below atmospheric pressure to such an extent as to cause the diaphragm 21 to move downwardly against the action of the coil spring 36 then the diaphragm will be effective to shift the balanced valve 22 to the dotted line position indicated at 39 allowing pressure to be released from the vent line Ii! into tank A to prevent collapse of the tank.

In tank B which is illustrated as serving merely as a storage chamber for the oil there may be existing a condition called thermo breathing due to temperature changes. Thus, this tank may lose its pressure at night or because of rainfall creating a long temperature drop resulting in condensation of vapors in the vapor space. Other ambient conditions may bring about a drop in pressure in tank B below atmospheric pressure. When this occurs therein to an extent as to cause the diaphragm 21 to descend against the action of the coil spring 36 pressure will be released from the vent line I0 into tank B thus protecting the tank against collapse. Conversely, if the pressure in tank B should rise due to a rising temperature this pressure will be confined or retained in tank B until such time as it reaches a degree to cause the diaphragm 21 to lift the weight 35. When this occurs excessive pressure in tank B is released into the vent line IU. However, until the pressure in tank B reaches this predetermined degree the diaphragm 21 will be held in its neutral position shown by the weight 35 and the valve 22 will thus be kept closed to conne the pressure in tank B until excessive pressure conditions have been' reached. In Figure 4 a modified or alternative form of construction is disclosed wherein the' diaphragm is generally Yindicated at 12M, connected to the buttery or damper type valve by means of the vstem 28a Vcorresponding t0 the stem 26. At the top of the housing the adl:justable .stem is illustrated at 32a and a .compression spring .40 is compressed between .the top of the housing .and a .holder tea which Aprovides a spring seat for the lower end of the spring 40. Downward movement `.of the holder 34a on the stem 32a is limited by the head 33a. :In -this form of construction like that illustrated in Fig. 2 upward movement of the diaphragm 21a is resisted above that position assumed by the diaphragm when the valve 22 is closed so that before the valve 22 will be opened by pressure existing in the tank the pressure therein must be Sneent to cause the diaphragm '21a to be forced upwardly with sufllciengt vforce to overcome the compression of the spring 40.

In situations where the tanks of the batteries :areof low pressure type such as bolted tanks, the maximum pressure allowable within-the tank `is normally within the neighborhood of two ounces. Consequently, in tanks of this character the use of a weight 35 as a means for resisting upward movement of the diaphragm is usually preferred. The weight is designed with relation to the size of the diaphragm so as to permit of opening of the valve 22 when pressure within the tank exceeds two ounces.

On the other hand, where the tanks of the battery are small welded tanks the pressure permissible within the tank is usually in the neighborhood of from 12 to 16 ounces. In such construction the use of spring 40 as a means for resisting upward movement of the diaphragm is usually preferred. The spring 36 is usually of such a character and is designed with relation to the diaphragm so as to permit downward movement of the diaphragm whenever the subatmospheric pressure exceeds one-half an ounce. In the case of tanks having higher working pressures the values given the weight 35, the spring 40 and the spring 36 may be proportional.

inasmuch as the vent line I in eifect functions somewhat as a storage reservoir for storing gas pressure released thereto from any tank having excessive pressure and to be discharged therefrom into a tank having subatmospheric pressure it is usually desirable to make the vent line l!! relatively large so as to be capable of containing a relatively large volume of gas. From the above described construction it will be appreciated that an improved vapor control system for storage tank batteries has been developed wherein any tank which has a negative or subatmospheric pressure even to a relatively low degree can receive gas pressure from the vent line to bring its pressure up to atmospheric or nearly so. Each tank, however, is closed to the vent line until such time as the pressure developed in the tank is a considerable degree above atmospheric pressure at which time pressure from the tank can be released into the vent line. The drop in pressure in any tank will not rob the vent line or the pressure existing in other tanks of the battery. If the pressure in the vent line materially exceeds the pressure in any 'tank such as the tank A, it will not escape therefrom into the tank A unless the pressure in tank A has fallen below atmospheric.

By means of the present system each tank of the battery is largely isolated from the other tanks thereof so as to conserve the gravity of the oil therein. Pressure is released from one tank 6,- of the battery int@ the yvent line only when presisure the .tank .exceeds a predeterminedvalue, Similarly. pressure in the vent line is released therefrom to any tank (only when the pressure in the `tank falls below .atmospheric pressure. While'the' valve-22 is illustrated as being of the butterfly or damper type it will be appreciated that other forms `of balanced valves may be substitutedtherefor if desired. A balanced valve or .one which is substantially balanced is highly desirable if any diierential in pressure between the yent'line I0 and a tank should be ineffective .to urge the valve to open.

'- 'f'Whi'le the valve embodying the present inventionis illustrated as 'being used between any or all tanks4 ofV a battery and their common vent line, Tit will be appreciated by those skilled in the .-'art'tlrat it may be used `on `a single tank between the tank and itsvent. Such a use mail befhighly advantageous, for example, on a gasolinestora'ge tank. -.Various changes maybe made in the 4details .0f construction without .departing from the spirit and scope of the invention as dened by the appended claims.

I claim:

1. In combination, a battery of storage tanks, a vent line connecting the tanks, a balanced Valve controlling communication between each tank and the vent line, a diaphragm operatively connected thereto exposed to pressure within the tank on one side and to atmospheric pressure on the other, and means for imposing a load on the diaphragm in opposition to the tank pressure applied thereto when the diaphragm attempts to move to a position to open the valve under the influence of tank pressure.

2. In combination, a battery of storage tanks, a vent line 'connecting the tanks, a balanced valve controlling communication between each tank and the vent line, pressure responsive means exposed to pressure within the tank and to atmospheric pressure for opening the balanced valve, and means for requiring a greater positive tank pressure to open the balanced valve than a negative tank pressure to open the valve.

3. In combination, a battery of storage tanks, a vent line connecting the tanks, a balanced valve controlling communication between each tank and the vent line, a diaphragm operatively connected to the balanced valve exposed to tank pressure on one side and to atmospheric pressure on the other, and means for resisting movement of the diaphragm under the influence of positive tank pressure beyond the position assumed by the diaphragm when the balanced valve is closed.

4. In combination, a battery of storage tanks, a vent line connecting the tanks, a balanced valve controlling communication between each tank and the vent line, a diaphragm operatively connected to the balanced valve exposed to tank pressure on one side and to atmospheric pressure on the other, and a weight engageable by the diaphragm for resisting movements of the diaphragm under the inuence of positive tank pressure beyond that position assumed by the diaphragm when the balanced valve is closed.

5. In combination, a battery of storage tanks, a vent line connecting the tanks, a balanced valve controlling communication between each tank and the vent line, a diaphragm operatively connected to the balanced valve exposed to tank pressure on one side and to atmospheric pressure on the other, and a spring engageable by the diaphragm for resisting its movement underA the iniiuence of positive tank pressure beyond that position assumed by the diaphragm when the balanced valve is closed.

6. A valve for controlling communication between the tanks of a battery and a vent line -to which they are connected comprising`a valve housing, a balanced valve in the housing controlling communication between the tank and the vent line, a diaphragm operatively connected to the balanced valve within the housing arranged to be exposed to tank pressure on one side and to atmospheric pressure on the other, and means for imposing a load on the diaphragm in opposition to positive tank pressure which becomes elective thereon only when the diaphragm moves under the influence of positive tank pressure beyond that position assumed thereby when the balanced valve is closed.

7. A valve for controlling communication between the tanks of a battery and a vent line to which they are connected comprising a valve housing, a balanced valve in the housing controlling communication between the tank and the vent line, a diaphragm operatively connected to the balanced valve within the housing arranged to be exposed to tank pressure on one side and to atmospheric pressure on the other, means for imposing a load on the diaphragm in opposition to positive tank pressure which becomes effective thereon only when the diaphragm moves under the iniluence of positive tank pressure beyond that position assumed thereby when the balanced valve is closed, and means for resisting movements of the diaphragm under the inuence of negative tank pressure.

CLARENCE D. LAIDLEY.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Spaeth Apr. 28, 1936 

